Certain apparatus or instruments enclosing electrical and/or electronic components can be used under conditions of shock, exposure to liquids, disinfection and strong chemical and physical aggression.
Such is particularly the case with electronic thermometers, particularly those used in a hospital environment.
However, these instruments are at present produced by assembly, for example by screwing, welding or snapping in, of two half shells or by assembly of a single shell body with a cap, the printed card or circuit supporting functional elements being first introduced into the body of these instruments.
As a result, there are joint lines and surface discontinuities, which constitute regions of weakness in terms of sealing, which can give rise to damage to the instrument, particularly when it is immersed for a prolonged period into a liquid, for example a disinfectant. Such instrument requires a long cleaning and disinfection time, which is troublesome for personnel in charge of this operation and for this reason often shortened.
There are known moreover techniques of production of pieces or elements by overmolding by injection of thermoplastic material, permitting creating pieces and elements resistant to shocks, compact and relatively sealed, without requiring recourse to fastidious and economically undesirable assembly processes.
However, the present overmolding techniques use wedging elements opening on the external surface of the overmolded piece and constitute discontinuities at this point, not permitting the overmolding of pieces sensitive to heat, or pressure, nor permitting a passage extending from the element to be overmolded to the external surface of the overmolded product. These techniques give rise to a large consumption of thermoplastic material, increasing the cost of production and the weight of the finished product.